The effect of inflammatory stimuli on the stroma of neoplasms: the involvement of mononuclear phagocytes.

The phlogistic response of the stroma supporting a transplantable rat fibrosarcoma and the ability of animals bearing a neoplasm to mount an inflammatory reaction to non-specific stimuli were investigated. In the unstimulated neoplasm the concentration of macrophages in the stroma was similar to that of normal connective tissue. The mononuclear exudate induced by cotton pellets or glass coverslips implanted in the neoplastic tissue, however, was reduced when compared with that in normal connective tissues at both 7 and 14 days after implantation of these foreign bodies. Since the emigration of radioactively labelled monocytes in both inflamed normal connective tissue and inflamed stromal tissue in the neoplasm proved to be similar, the assumption has been made that neoplastic cells inhibit the local accumulation of the newly emigrated monocytes. This macrophage dispersing effect only occurs in the neoplasm and there is no systemic action. The only systemic effect detected is an anti-inflammatory action which was significant only between the 1st and the 2nd wk after transplantation of the neoplasm into neonatal recipients.